Comment on "Solute transport under non-linear sorption and decay.".
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Adsorption↗
Biomedical subjects
D A Barry
Publications and source records attributed to D A Barry.
Cadmium desorption in sand.
Desorption of cadmium (Cd) from sand was studied by both batch and flow-through methods. Batch experiments were conducted at three pH values (5.5, 6.0 and 6.5). In each case, the amount of Cd desorbed was low compared with the quantity of Cd adsorbed previously. Desorption of Cd in the batch experiments can be described adequately by a Freundlich isotherm. The Freundlich isotherm coefficient, Kf, increased with pH. Hysteresis between the sorption/desorption isotherms was observed in all batch experiments. Flow-through experiments in soil columns were conducted for the same three pH values, with the results used to determine transport and sorption/desorption parameters. Again, the desorption isotherms bore little resemblance to the corresponding adsorption isotherms. The experimental breakthrough curves were well fitted by a nonequilibrium desorption model, however the time scale of the desorption process was much larger than measured in batch experiments. This model was therefore rejected as lacking realism. A simple linear retardation (including hysteresis) model that utilises different isotherms was found to simulate column breakthrough curves well. The Freundlich isotherm coefficients, Kf, in all batch and flow-through desorption experiments were different to values evaluated from the corresponding adsorption experiments. However, in contrast to adsorption, desorption in flow-through experiments was not noticeably affected by changes in pH. The effect of pore-water velocity on desorption was also studied at pH 6.0. No trend was established between flow velocity and the desorption coefficient.
Adsorption↗
Modelling of physical and reactive processes during biodegradation of a hydrocarbon plume under transient groundwater flow conditions.
Numerical experiments of non-reactive and reactive transport were carried out to quantify the influence of a seasonally varying, transient flow field on transport and natural attenuation at a hydrocarbon-contaminated field site. Different numerical schemes for solving advective transport were compared to assess their capability to model low transversal dispersivities in transient flow fields. For the field site, it is shown that vertical plume spreading is largely inhibited, particularly if sorption is taken into account. For the reactive simulations, a biodegradation reaction module for the geochemical transport model PHT3D was developed. Results of the reactive transport simulations show that under the site-specific conditions the temporal variations in groundwater flow do, to a modest extent, affect average biodegradation rates and average total (dissolved) contaminant mass in the aquifer. The model simulations demonstrate that the seasonal variability in groundwater flow only results in significantly enhanced biodegradation rates when a differential sorption of electron donor (toluene) and electron acceptor (sulfate) is assumed.
Biodegradation, Environmental↗
Cross-sectional study of the association of abomasal displacement or volvulus with serum electrolyte and mineral concentrations in dairy cows.
The objective of this study was to evaluate serum mineral and electrolyte concentrations at the time of on-farm diagnosis of left displaced abomasum, right displaced abomasum, or abomasal volvulus in dairy cows. Data were collected from 104 affected cows and 96 control cows matched with cases, based on herd, parity, and stage of lactation. Cows with abomasal displacement or volvulus had significantly lower calcium, phosphorous, magnesium, potassium, and chloride concentrations and increased anion gap at the time of diagnosis compared with control cows from the same herds. The percentages of cases and controls with total serum calcium concentrations below the lower limit of the laboratory reference range (2.08 mmol/L [8.3 mg/dL]) were 70% and 23%, respectively. Based on the large percentage of cases with hypocalcemia, administering calcium salts at the time of treatment of field cases of abomasal displacement or volvulus may be beneficial.
Abomasum↗
Casein kinase II-mediated phosphorylation of the C terminus of Sp1 decreases its DNA binding activity.
We have previously observed that Sp1, a ubiquitous zinc finger transcription factor, is phosphorylated during terminal differentiation in the whole animal, and this results in decreased DNA binding activity (Leggett, R. W., Armstrong, S. A., Barry, D., and Mueller, C. R. (1995) J. Biol. Chem. 270, 25879-25884). In this study, we demonstrate that casein kinase II (CKII) is able to phosphorylate the C terminus of Sp1 and results in a decrease in DNA binding activity. This suggests that CKII may be responsible for the observed regulation of Sp1. Mutation of a consensus CKII site at amino acid 579, within the second zinc finger, eliminates phosphorylation of this site and the CKII-mediated inhibition of Sp1 binding. Phosphopeptide analysis confirms the presence of a CKII site at Thr-579 as well as additional sites within the C terminus. No gross changes in CKII subunit levels were seen during de-differentiation associated with liver regeneration. The serine/threonine phosphatase PP1 was identified as the endogenous liver nuclear protein able to dephosphorylate Sp1 but again no gross changes in activity were observed in the regenerating liver. Okadaic acid treatment of K562 cells increases Sp1 phosphorylation and inhibits its DNA binding activity suggesting that steady state levels of Sp1 phosphorylation are established by a balance between kinase and phosphatase activities.
Amino Acid Sequence↗
MODFLOW/MT3DMS-based reactive multicomponent transport modeling.
This paper presents a three-dimensional, MODFLOW/MT3DMS-based reactive multicomponent transport model for saturated porous media. Based on a split-operator technique, the model, referred to as PHT3D, couples the transport simulator MT3DMS and the geochemical modeling code PHREEQC-2. Through the flexible, generic nature of PHREEQC-2, PHT3D can handle a broad range of equilibrium and kinetically controlled reactive processes, including aqueous complexation, mineral precipitation/dissolution, and ion exchange. The diversity of potential applications is demonstrated through simulation of five existing literature benchmarks and a new three-dimensional sample problem. The model might be applied to simulate the geochemical evolution of pristine and contaminated aquifers as well as their cleanup. The latter problem class includes the natural and enhanced attenuation/remediation schemes of a wide range of organic and inorganic contaminants. Processes/reactions not included in the standard PHREEQC-2 database but typical for this type of application (e.g., NAPL dissolution, microbial growth/decay) can be defined and included via the extensible PHREEQC-2 database file.
Benchmarking↗
The relationship between E. coli indicator bacteria in well-water and gastrointestinal illnesses in rural families.
OBJECTIVES: To determine the relationship between consumption of E. coli contaminated well-water and gastrointestinal illness in rural families. METHODS: One hundred and eighty-one families with well-water as a drinking source participated in a one-year follow-up study. Water was tested for E. coli bacteria and health outcomes were monitored for house-hold members. RESULTS: E. coli in well-water was significantly associated with gastrointestinal illness in family members, however the relationship was modified by the distance from the septic tank to the well. E. coli had an odds ratio of 2.16 [95% CI 1.04, 4.42] if the septic tank was greater than 20 metres from the well and 0.46 [95% CI 0.07, 2.95] if the septic tank was within 20 metres. CONCLUSIONS: Consumption of contaminated well-water is associated with gastrointestinal illness. E. coli can be a useful marker for detecting wells that pose a potential public health problem in rural areas.
Adolescent↗